linux-kernel - Re: [PATCH v2 15/16] objtool/powerpc: Enable objtool to be built on ppc

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Date:   Thu, 1 Sep 2022 16:38:52 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Segher Boessenkool <segher@...nel.crashing.org>
CC:     Sathvika Vasireddy <sv@...ux.ibm.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "aik@...abs.ru" <aik@...abs.ru>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "npiggin@...il.com" <npiggin@...il.com>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "naveen.n.rao@...ux.vnet.ibm.com" <naveen.n.rao@...ux.vnet.ibm.com>,
        "mbenes@...e.cz" <mbenes@...e.cz>,
        "chenzhongjin@...wei.com" <chenzhongjin@...wei.com>
Subject: Re: [PATCH v2 15/16] objtool/powerpc: Enable objtool to be built on
 ppc



Le 01/09/2022 à 17:11, Segher Boessenkool a écrit :
> On Thu, Sep 01, 2022 at 09:32:46AM +0000, Christophe Leroy wrote:
>> Le 29/08/2022 à 07:52, Sathvika Vasireddy a écrit :
>>> +int arch_decode_instruction(struct objtool_file *file, const struct section *sec,
>>> +			    unsigned long offset, unsigned int maxlen,
>>> +			    unsigned int *len, enum insn_type *type,
>>> +			    unsigned long *immediate,
>>> +			    struct list_head *ops_list)
>>> +{
>>> +	u32 insn;
>>> +
>>> +	*immediate = 0;
>>> +	insn = bswap_if_needed(file->elf, *(u32 *)(sec->data->d_buf + offset));
>>> +	*len = 4;
>>
>> Should be *len = 8 when insn >> 26 == 1.
> 
> But please use ppc_inst_prefixed().  And just use ppc_inst_len() here?

objtool is a userland app, there is no access to kernel headers here.

> 
> Not having convenience abstraction functions like that will give you
> much more work in the future -- currently all prefix insns use primary
> opcode 1, sure, and nothing else does; but this can change.
> 

Yes most likely. Then we have to rebuild some light abstraction for objtool.

Christophe